THE PRESENT INVENTION relates to an air-bag and more particularly relates to an air-bag intended for use in a vehicle such as a motor car.
It has been proposed previously to provide air-bags in motor vehicles such as motor cars, the air-bags being adapted to be inflated in the event that an accident should occur.
A typical air-bag is made of a fabric, such as a woven polyamide material, and the air-bag is adapted to be inflated very rapidly in response to a signal which senses an impact or an accident situation.
Typically, such air-bags are located in the steering wheel or in the dash-board to provide protection for an occupant of the vehicle in the event that a frontal impact should occur. Such air-bags are inflated relatively rapidly and commence deflation almost immediately so as to provide a soft cushion. A soft cushion tends to decelerate an occupant of a vehicle, when the occupant is thrown forwardly during a frontal impact, without injuring the occupant.
Air-bags of the type described above are generally inflated in a period of time which is less than 50 milliseconds, and often the air-bag is substantially deflated 200 milliseconds after the impact is sensed. Consequently, air-bags of this type do not provide sustained protection, which may be desirable in the event of a roll-over accident and which may also be desirable in the event that a second impact should occur following an initial impact.
It has been proposed (see WO96/22199) to use a metal air-bag with a separate gas generator. The described metal air-bag is of a complex design and difficult to manufacture. A similar air-bag is disclosed in U.S. Pat. No. 5,868,422. U.S. Pat. No. 3,425,712 discloses an air-bag with a gas generator located within the air-bag.
The present invention seeks to provide an improved air-bag arrangement.
According to this invention there is provided an air-bag, said air-bag comprising a first metal layer and a second metal layer super-imposed on the first layer, at least one of said layers being plastically deformable, the layers being provided with a peripheral seal sealing the layers together to define a substantially gas-tight chamber, there being gas generating means within the chamber and means to activate the gas generating means, wherein the gas generating means are retained in position by regions of the said two layers where the two layers are secured together.
The metal may be coated with plastic or laminated in some other way.
The metal layers preferably have a very low permeability. The air-bag, when inflated, may remain inflated for a relatively long period of time, thus providing sustained protection. The use of metal may also provide the advantages of corrosion resistance and wear resistance.
Preferably the first chamber is substantially gas-tight.
Advantageously both of the layers are plastically deformable.
Advantageously the gas generating means are retained in position in a respective chamber that communicates with the first chamber.
Conveniently the gas generating means comprise pyrotechnic means, and the means to activate the gas generating means comprise means to ignite the pyrotechnic means.
Preferably the pyrotechnic means comprise an igniter adapted to be ignited in response to an electrical signal, and an inflator adapted to be activated in response to activation of the igniter.
Advantageously the igniter comprises a pyrotechnic charge within a housing formed of a plastics material.
Conveniently the inflator comprises a pyrotechnic charge within a housing of a plastic material.
Preferably the igniter and the inflator are located in adjacent recesses defined by the said first metal layer and second metal layer, with there being a passage between the two recesses providing a communication between the recesses.
Conveniently the chamber is divided into a plurality of inter-communicating cells by a plurality of regions in which the first layer is secured to the second layer.
Preferably in the regions where the first layer is secured to the second layer, the first layer is welded to the second layer.
Advantageously the peripheral seal is constituted by a peripheral weld.